<<
That doesn't make a lot of sense. >>
Yes, it does, if you understand the products, the science behind them... and the fact that
BiggDog implied (but didn't state) that the heatsink was to be mounted FIRST. When I say that he implied it, common sense would dictate that a) the compound on the bottom of the heatsink wouldn't be altered unless it were in contact with the CPU, and b) why unplug the fan if the heatsink weren't mounted in the first place?
Anyway... on to the explanation.
The square of gummy stuff, often pink in color, is thermal interface material with phase change characteristics. What this means, is that it is a bit hard but sticky before it is installed properly. After proper installation, which usually requires the chip to get up to the 55C range, the material is permanently altered to a VERY gummy, sticky substance. The advantage of this is that you can apply the substance to a surface, like the bottom of a heatsink, from a roll of precut squares and it isn't a total mess. Later, when subjected to the proper heat, the substance melts down and becomes more liquidy... at that point it gently flows into every nook and cranny between the heatsink and the CPU, and stays there permantent making contact and filling all of the heat holding thermal voids. If you ever remove an AMD CPU that has been properly installed with the stuff you can pretty much read all of the CPU etchings in the gum, only in reversed letters.
The standard way to apply the stuff is to insert your CPU and heatsink as normal, but with the CPU fan unplugged. Boot the machine and go into the BIOS area of your motherboard that has the hardware monitoring. Wait at the temperatures climb because of no having the fan blowing (note, this is NOT the same as not having a heatsink installed... with a good heatsink it still takes a couple of minutes for the CPU to get up to the 55C needed). Once the temperature reached 55C, exit your BIOS and turn the machine off. The phase change has now taken place. Plug your fan back in and proceed as normal.
I don't have time to give you all of the background for all of the different companies that make these materials, but I figured that I should provide something, so I snatched the data from
Thermagon, who is the manufactured of the gum that ThermalTake uses. Information about the line of phase change materials can be found
Here. There are also a couple of PDF's that have more detailed info.... I'll give you a couple of the highlights:
<<
T-pcm 900 Series? is a high performance, non-electrically conductive phase change material. At 50°C, T-pcm begins to soften and flow, filling the microscopic irregularities of both the thermal solution and the integrated circuit package surfaces, thereby reducing thermal interface resistance. T-pcm 900 is a flexible solid at room temperature and freestanding without reinforcing components that reduce thermal performance. >>
And From One Of The PDF's
<<
3. For parts individually cut:
b. Remove one liner and position the part onto the thermal solution. There is about
a 1-2 minute dwell time in which T-pcm will wet to the thermal solution surface.
c. Once the thermal solution is ready to be assembled the top liner should be
removed.
4. Once the device has been mounted, the T-pcm will soften and fill the interstitial
voids on the parts surfaces when heated to 50-70°C. This serves to decrease the
contact thermal resistance between the parts and thus, reduce the overall thermal
resistance.
5. After the first time T-pcm goes through its phase change between 50-70°C the
interface thickness will be set and the interface resistance will remain constant. >>
Hope this clears the matter up.
BTW, just for future knowledge, although all of us are fallible, BiggDog has been around for a LONG time. I've dealt with him since before the internet was even popular, when my machine was a 386sx with 4 megs of RAM and 97 Megs of Hard Drive space (two drives). He's built
dozens and dozens[/b] of machines of all varieties for well over a decade. He's also been a valued member of these boards LONG before we had 2500 members. He did leave out being blatant about needing the heatsink in place, but in general, if he gives you the info on how to do something with a computer, you can take it to the bank.
Joe
